Magma ASIC Design Flow
Magma For You in Three Hours (MYTH) - Hour I
MYTH is not a myth
V. Kamakoti and Shankar Balachandran
Reconfigurable Intelligent Systems Engineering Lab
Department of CSE, IIT Madras

 

1. About The Document:
This document briefly explains the usage of Magma Electronic Design Automation (EDA) Tool for the design of the Application Specific Integrated Circuit (ASIC) Flow. This tool will take you from Register Transfer Level (RTL) to Graphical Design Standard II (GDSII) format.

2. The basic requirement to use this document:
This document is prepared aiming the person with little digital circuit design knowledge using any HDL language. Assuming the person is aware of the ASIC Design flow and Digital Optimization techniques (Is explained briefly below).

3. Introduction to ASIC Design Flow:
Any IC other than a general purpose IC which contain the functionality of thousands of gates is usually called an ASIC (Application Specific Integrated Circuit). ASICs are designed to fit a certain application. An ASIC is a digital or mixed-signal circuit designed to meet specifications set by a specific project. The basic ASIC Design Flow is Shown in Figure 3.1.

Figure 3.1: ASIC Design Flow

Figure 3.2: EDA Tool Flow for ASIC Design

The EDA Tool that is used for synthesis of a RTL code to GDS II format is Magma Blast Fusion. The details of the Magma Design Flow is explained below

4. Introduction Magma ASIC Design Flow:
Blast Plan Pro is used for the hierarchical design of large integrated circuits (ICs) and systems-on-chip (SoCs) with Magma's production-proven RTL-to-GDSII flow. Hierarchical design methodologies are typically adopted to handle very large designs or to support the concurrent design of a complex chip by a design team. Blast Plan Pro meets both of these requirements and delivers the additional benefit of predictable design closure.

The Magma tools form an integrated set of design engines that are combined with a Tcl interpreter and a sophisticated graphical user interface (GUI). These tools are software applications developed and distributed by Magma Design Automation Incorporated.

The typical simplified design flow of the Magma Blast Fusion is shown in the below Figure 3.

This tutorial describes how to use the Magma Blast Fusion using command prompt to run these steps on a provided design. Follow the instructions provided in this tutorial to create scripts that perform the steps for the provided design.

The following Figure 4 shows the structure of this tutorial. The instructions for importing the design and constraints depend on whether you start from a netlist or from RTL. After you import the design and constraints, the remaining flow steps are the same.

These instructions use only the options applicable to the provided design, but the other options in the command prompt are operational. The Magma tool flow supports design entry using the GUI mode and Text mode. The RTL to GDSII flow is explained using a sequential circuit.

5. The Magma RTL to GDSII using command prompt:

The detailed flow is explained in the three stages as follows:

Stage 1: Invoking Mantle, Import RTL Design and Imoport Design Constraints

Invoking Mantle

Step - 1: Create a directory where you want put all your magma synthesis documents. In this example, aes is the working directory.

bash-2.05b$ mkdir aes

This will create a directory called "aes" . Copy your all RTL Code in to the created directory. Then go to the directory to invoke the magma tool.

bash-2.05b$ cd aes

Step - 2: Invoke the mantle using the path "/magma/2004_12_29.0014/linux24_x86_64/bin/mantle". Mantle is the command prompt of the Magma Blast Fusion Tool.

bash-2.05b$ /magma/2004_12_29.0014/linux24_x86_64/bin/mantle
 MEM-4    WARNING: Unusually large stacksize of 17592186044416.0MB reserved by
         user's shell resource limits. This may inhibit utilization of all
         available system memory resources.  Recommended is 8000k
Copyright (C) 1997-2004 Magma Design Automation Inc.
mantle version 4.1.57-linux24_x86_64 (compiled Dec 28 2004 23:43:34)

LIC-1    Setting default license file to
         '/magma/2004_12_29.0014/common/license'.
LIC-12   The following features have been checked out: BLAST_VIEW BLAST_WRAP
         BLAST_SPEED BLAST_BUILDER BLAST_PLAN BLAST_RTL BLAST_LOGIC BLAST_SI
         BLAST_RAIL
OSD-100  Running /magma/2004_12_29.0014/linux24_x86_64/bin/mantle on host
         "vlsi2" with pid 30575 for user "temp" started on Thu Mar 01
         01:18:55 PM IST 2007 in directory /home/temp/noors/aes
mantle[1]>

Note: If you have any problem in opening the mantle please contact to CS623 TAs. If you come across any error stating Error UI-39 in invoking the tool ask System Administrator to run "nscd" demon. If you come across any license related problems, then use "export LM_LICENSE_FILE=2700@10.6.5.27" at your command prompt. Still if you have any problem please contact System Administrator.

Directory Structure Generated by Magma

Files generated by Magma: You can also review the contents of two automatically-generated directories. The logfiles directory contains logs of the sessions you run, and the snap directory contains volcanos and reports of design statistics that reflect the design at the end of each part of the flow.

Logfiles Directory: When you start the tool, a file called mantle.log is created. This file is usually the most useful file in the logfiles directory. It contains a full record of your latest session. With each new session you start, the file is renamed to mantle#.log (# is a number) and the mantle.log file is overwritten with the latest information. In the tool, to find where the file has been saved, use the query logfile command.

Snap Directory: The snap directory is created locally in the directory where you have started the tool. This directory stores snapshot volcanos and status reports that show design statistics during the flow. Use a text editor to review the snapshot reports or use a snapshot volcano to rerun the flow from a specific step. There are several config, query and report commands related to snap, which are identified in the man pages.

Step - 3: To invoke the Graphical User Interface (GUI) use the following command.

mantle[1]> ui start

The above command will opens the GUI based work space of the Magma Blast Fusion as shown in the Figure 5.1.

Importing the Library Volcano

To use the provided design library, import the library and technology rules together in the form of a Volcano. A Volcano is a Magma database that stores design information.

Step - 4: Import the library using the following command where all the logic cells are stored. (Please verify the library path with course TA). In this example we are using the Magma 130nm library cell for synthesis. Import volcano command reads the data model from a disk.

mantle[0]:> import volcano /magma/cl013lv.volcano
mantle[0]:>import volcano /magma/cl013lv.volcano
MSG-10 While running 'import volcano /magma/cl013lv.volcano':
LAVA-333 This volcano erupted Tue Jan 21 12:42:38 2003 EST for user jwalston (Joe Walston)
(v14c1)
LAVA-24 'import volcano' importing global config settings from volcano, existing settings
maybe overwritten
LAVA-27 Reading library /cl013lv
LAVA-874 All cells were bound as a result of this 'import volcano'.
LAVA-902 Melted back from volcano '/magma/cl013lv.volcano' ( 2 seconds elapsed of which
2 on CPU).
LAVA-249 Volcano file size: 34.6 MByte (57.1 MB data, Compression = 1.65x)
LAVA-251 Data throughput 21.631 MB/s (2.64 s elapsed)

"Set l " set the variable for library name. The library name that we are using is cl013lv.

mantle[0]:>set l /cl013lv
mantle[0]:>set l /cl013lv
/cl013lv

Import the RTL Design

Step - 5: Now import your RTL code in a sequence of top module file is followed by the rest of the design files. For purpose of clear explanation here we are using a standard AES design. It is designed using verilog and whose topmodule name is "aes_cipher_top". AES design contains the following verilog files.

aes_cipher_top.v (Top Module)
aes_sbox.v
aes_rcon.v
aes_key_expand_128.v

Step - 6: "import rtl" reads the RTL files. To analyze RTL code use "-analyze" at the end. "-analyze" is optional command.

mantle[0]:> import rtl aes_cipher_top.v aes_sbox.v aes_rcon.v aes_key_expand_128.v
mantle[0]:>import rtl aes_cipher_top.v  aes_sbox.v aes_rcon.v aes_key_expand_128.v
MSG-10 While running 'import rtl aes_cipher_top.v aes_sbox.v aes_rcon.v
aes_key_expand_128.v':
RTL-3 Building model aes_cipher_top(aes_cipher_top)
RTL-3 Building model aes_key_expand_128(aes_key_expand_128)
RTL-3 Building model aes_sbox(aes_sbox)
RTL-3 Building model aes_rcon(aes_rcon)
/work/aes_cipher_top/aes_cipher_top

Step - 7: "set m" set the variable for the top level Design. In this design the top level model is "/work/aes_cipher_top/aes_cipher_top". The top level model path is displayed at the end of the report of the "import rtl" command.

mantle[0]:>set m /work/aes_cipher_top/aes_cipher_top
mantle[4]:>set m /work/aes_cipher_top/aes_cipher_top
/work/aes_cipher_top/aes_cipher_top

Step - 8: "fix rtl" performs RTL optimizations.

mantle[5]:> fix rtl $m

To See the mantle Report click here

Step - 9: "fix netlist" performs the logical optimizations.

mantle[5]:> fix netlist $m $l

To See the mantle Report click here

Step - 10: "export verilog netlist" saves the verilog netlist file to specified file name for example "filename_netlist.v". The proper usage of export command is shown below.

mantle[5]:> export verilog netlist $m aes_cipher_top_netlist.v

To See the mantle Report click here

Note: The Netlist to GDSII flow will start from next point. You can import any netlist file to the magma flow.

Step - 11: "run bind logical" will bind the unbound cells to the target library.

mantle[5]:> run bind logical $m $l

To See the mantle Report click here

Step - 12: "report model" Checks the model for basic netlist and floorplan integrity (for example, cell overlap and dangling input pins, etc.,).

mantle[5]:> report model $m

To See the mantle Report click here

Now you can see the circuit model schematic by selecting the "Open Schmatic viewer" in the "Viewers" tab of the GUI. It will ask the schematic model name, Specify the model name in this design example is "/work/aes_cipher_top/aes_cipher_top". The schematic diagram of the whole design (AES) is shown in Schematic1, Schematic2 (zoom) and Schematic3 (zoom), Schematic4 (zoom), and worst path in Schematic viewer.

Import Design Constraints

Import the design constraints to review a timing check and timing report to make sure the constraints are complete and to establish a timing baseline for later comparison.

Step - 13: "force timing clock" will assign the timing constraint to the clock. To estimate the Worst late slack assign the clock period, rise and fall times of the clock. In this design example we are assigning the clock period as 1000ns (1 MHz clock) and, rise and fall times are 5ns and 10ns respectively.

Note: This command is used only in case of sequential circuits. (This command is not required in case of combinational circuit ). In general the combinational ciruit will have the +INF worst late slack.

mantle[11]:> force timing clock {/work/aes_cipher_top/aes_cipher_top/mpin:clk} 1000n -waveform {-rise 5n -fall 10n}

Step - 14: "report force timing" will report the timing summary for the forced or defined clock signal.

mantle[11]:> report force timing $m

To See the mantle Report click here

Step - 15: "force wire model" will defines the design wire model to either constant or wireload model. In this design example we are defining the wire model as a constant model using the following command.

mantle[11]:> force wire model constant $m

Step - 16: "report timing summary" will generates a timing analysis summary report for the model.

mantle[11]:> report timing summary $m

To See the mantle Report click here

Note: In general, check the timing summary report and find what is value of Worst Late Slack. If it is positive with small integer then proceed to next step (try to make the worst late slack as either 0 or 1). If the worst late slack is negative then make it positive by varying the timing information that is defined for the clock (Period, Rise and Fall times). Do this until you get the positive slack (0 is preferred). Make the iterative run of the previous three commands to get the positive slack of significant amount. The following report will give the idea of how to achieve the significant positive slack.
To See the mantle Report click here

Step - 17: "check timing" will Checks and reports on the completeness of the timing constraints.

mantle[38]:> check timing $m

To See the mantle Report click here

Step - 18: "data flatten" will flattens the hierarchy under a model or cell.

mantle[38]:> data flatten $m

Step - 19: "run gate sweep" will Successively eliminates all unreachable cells, single-input cells, and constant cells from the design.

mantle[38]:> run gate sweep $m

To See the mantle Report click here

 

Lecture 39: Logic Optimization, Floor Planing and Power Planning.

Lecture 40: Physical Optimization, Clock Design and Detailed Routing.

Note: Adding IO Pads to the chip is not explained in this tutorial.

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